\documentclass[a4paper, 12pt]{article}

\begin{document}

\section*{Section Headings}

We explain in this section how to obtain headings for the various sections and subsections of our document.

\subsection{Headings in the `article' Document Style}

In the `article' style, the document may be divided up into sections, subsections and subsubsections, and each can be given a title, printed in a boldface font,
simply by issuing the appropriate command.

\subsubsection*{Hello World}

\end{document}
